Currently, there are no recommendations or guidelines concerning the preferred diameter of esophageal stents for palliative treatment, owing to the lack of adequate evidence. We therefore conducted a retrospective cohort study to evaluate whether 18 mm stents would achieve a similar function of dysphagia relief with fewer complications and longer survival compared to 20 mm stents. Esophageal cancer patients who underwent 125 iodine seed-loaded stent placement with a diameter of either 18 mm (n = 103) or 20 mm (n = 54) were included at five hospitals in China. The stabilized inverse probability of treatment weighting (IPTW) was used to control potential confounding factors and bias that are inherent in a retrospective study. The primary endpoint was dysphagia relief. Stent-related complications and overall survival were assessed as the secondary endpoints. In the IPTW-adjusted analysis, no significant difference was found in the dysphagia score between the two groups either at 1 week after stent placement or at the last week before death. Despite a comparable rate of overall complications, there was a significantly lower incidence of severe retrosternal pain (15.4% vs. 32.7%,p = 0.013) and a trend toward longer survival (median survival, 176 days [95% confidence interval (CI) 144 to 209] vs. 109 days [92 to 126],p = 0.057) in the 18 mm group. An irradiated stent with a diameter of 18 mm showed a similar outcome of dysphagia relief to that achieved with a 20 mm diameter stent, but halved the incidence of retrosternal pain after stent placement.